The invention relates to a circuit arrangement for locking and/or unlocking a door lock, especially in an electric appliance that is provided with a door for closing or opening a work area, with an electrically-controllable door lock actuator which acts upon a locking member which locks or unlocks the door lock when a current flows through the actuator. With an electric appliance, such as an electric washing machine for example, such an electrically-controllable door lock is as a rule combined with a mechanically-actuatable door lock with which a door for closing or opening the work area of the relevant appliance is provided. Depending on its embodiment, the electrically-controllable door lock, once activated, acts on the mechanically-actuated door lock so that said lock cannot be actuated until the electrically-controlled door lock is either activated once again or is deactivated again.
A door with an electromagnetic closing/opening apparatus, especially for washing machines, is already known (DE OS 1 610 247), in which a lock connected to the housing of the washing machine possesses a bolt which engages with a lug on the door. The relevant bolt is released by means of an electromagnet controllable by a control device of the washing machine for opening said door or is secured for locking the relevant door. In this case an opening of the relevant door after the washing machine is put into operation is only possible after a delay, and only then once the washing machine has been stopped and the water drained out. However nothing is known in this connection about any measures for monitoring the operability of said control device during the activation of the electromagnetic opening device.
An electromagnetically-actuatable door lock device for washing machine is also known (DE-OS 2 106 273), which uses a bimetal heated swing bolt to lock a locking latch of the door closure device such that the door cannot be opened. Only after the bimetal strip has cooled off again after the washing process and the locking latch releases can be washing machine door be opened. In this context too nothing is known about any measures for monitoring the operability of a control device controlling the door locking device.
A device for locking the door of a washing machine or a dishwasher is also already known (DE 196 01 228 A1), in which a locking element is provided, which is able to be moved into an open position in which it releases a door hook of the door to open said door, and which is able to be moved into a closing position in which it blocks the door hook at a door opening. Locking and unlocking positions of the locking element are controllable by means of a bistable pre-stressed element and a locking bolt. The said locking bolt is able to be moved by the bistable element so as to engage with the locking element in order to fix the latter in a closed position. The bistable element also pushes the locking bolt into an open position in which this is free from the locking element. The relevant known device thus features a bistable element which can be pre-stressed in two positions: In one position a movement of the locking element from its closed position into its open position is prevented, and in the other position a movement of the locking element from is closed position into its open position is enabled. However in this connection too nothing is specified about any measures for monitoring the operability of a control device controlling the relevant device.